It is not easy to remove a bubble in highly viscous fluid because of its viscosity, and various defoaming methods have been used. (See Patent Literatures 1 to 6, and Non-patent Literatures 1 and 2).
With respect to this type of known technology, in order to efficiently remove a bubble included in a liquid, the applicant of the present application proposed a “Bubble Removal Method and Bubble Removal Device” as disclosed in PTL 7. This method is a bubble removal method that continuously removes bubbles. The method uses a vessel which has one or more inlets and two or more outlets and which has a structure that allows its volumetric capacity to be varied. The method allows non-Newtonian fluid to pass through the vessel and changes the volumetric capacity of the non-Newtonian fluid in the vessel by vibration to depressurize and pressurize the interior of the vessel, thus increasing and decreasing the volume of a bubble contained in the non-Newtonian fluid and causing the bubble to move to a specific outlet. The method is characterized by performing depressurization and pressurization inside the vessel while the pressure changes are maintained inside the vessel by means for maintaining the flow resistance that are provided on each of the inlet and the outlets.